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Pilot Jet Circuit 101?

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I'm getting so frustrated with this that pretty soon either me or the DRZ is going over a cliff. :naughty:

I'm running the burned jetting.

DXP clip 5

40 PJ

PAS ~1/2 turn

Fuel Screw ~3 turns

MJ 148

MAJ 200

Coast enrichener removed

Typical riding day is 0-20C (32-70F) altitude is 4000 ft.

I think the MJ is a little fat for my altitude?

Bike runs well from mid to top, with a very slight off idle bog, more just lazy than a bog.

My problem is the pilot circuit. Burned jetting calls for a 38 PJ and 1/2 to 5/8 PAS, I went to the 40 and 1/2 PAS because it was so lean. It's still too lean. Pops like crazy on decel when warm, even backfires and causes it to stall. It will stall if the fuel screw is turned in to 1.5 turns or less, and I've got a hanging idle problem as well. All symptoms of the pilot circuit still being too lean?

The carb is clean to the best of my knowledge, I've soaked it and blown it out twice. What could be causing what seems to be a very abnormal lean condition in my pilot circuit?

I'm going to try going up to a 45 PJ tonight after work because even at 40, the bike is obviously lean, but it seems crazy since everyone else is running a 38.

I'd appreciate any thoughts.

Waxy

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Your logic is right on. But given your jetting, the problem is not in your choice of jets. It is lean for some other reason. Air leak. Are all the un-used nipples sealed? Is the carb in he rubber boot all the way? Defective carb or parts? The PAS really set - 5/8 turn. Try fixed jets 38/70, 45 or 48/100. Is the floating slide plate in the right way? (center notch down) and is the seal between the roller slide and the floating plate in good condition? Is the top sealed to the body? (should not really make a difference but it might) You can try really rich on the pilot circuit (like 48/60) but if that doesn't make it blubber, you know it is something else.

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Your logic is right on. But given your jetting, the problem is not in your choice of jets. It is lean for some other reason. Air leak. Are all the un-used nipples sealed? Is the carb in he rubber boot all the way? Defective carb or parts? The PAS really set - 5/8 turn. Try fixed jets 38/70, 45 or 48/100. Is the floating slide plate in the right way? (center notch down) and is the seal between the roller slide and the floating plate in good condition? Is the top sealed to the body? (should not really make a difference but it might) You can try really rich on the pilot circuit (like 48/60) but if that doesn't make it blubber, you know it is something else.

That's what I kept thinking.

I'll have to construct a checklist of possible problems.

I know the carb is well sealed into both rubber boots.

I'll check the unused nipples, but I'm pretty sure they're all sealed with rubber automotive vacuum port plugs.

Floating slide plate? Roller slide? I'm not sure what you mean, but I've never had the slide out of the carb.

So far the adjustments to the PAS have done nothing, so it might be the problem. The only other problem I can think of would be plugged vanes in the carb, or a plugged PJ, and I've cleaned them both thoroughly. :naughty:

I'll try taking it out and going with the stock PAJ and the 45 PJ tonight and report back.

Any other ideas?

Thanks,

Waxy

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PAS - you do mean SUDCO replacement for the pilot air jet located in the air bell? The one that replaced the 60 air jet. It definitely should have an affect. Some people report little affect from the fuel screw located under the carb (including me) but I have not figured out why. However, with that condition, it still runs OK. You can rig your bike to run with the PAS exposed so you can make adjustments running.

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PAS - you do mean SUDCO replacement for the pilot air jet located in the air bell? The one that replaced the 60 air jet. It definitely should have an affect. Some people report little affect from the fuel screw located under the carb (including me) but I have not figured out why. However, with that condition, it still runs OK. You can rig your bike to run with the PAS exposed so you can make adjustments running.

Yes, the replacement for the PAJ from sudco. It seemed to have some effect if really opened up, ~1 turn, but from ~5/8 down to 3/8 or less, it doesn't seem to have much effect.

I have the Kientech extended fuel screw, and as I said, the bike will stall if it's screwed in to ~1.5 turns or less. According to the literature, this means the PJ is too small. Again, I'm running a 40, and the "standard" seems to be a 38, so it seems weird.

Waxy

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I went back to the stock 45PJ and fixed 60 PAJ.

Overall, an improvement, it definitely idles better and there's very little pop on decel, I think performance in the low end is better as well.

However, it now runs like stock. :naughty:

It has the slight stumble/bog off idle/low end. Runs great mid range to top though.

It's still giving me some signs of being lean believe it or not. I can get the bike to stall out if I turn the fuel screw in to about 1 turn or so, it starts running rough at about 2 turns. If I turn it out to about 3-3.5 turns, it idles nicely. Once completely warmed up, it does have a very slight hanging idle too.

This amazes me, I thought it would be really rich. I'm starting to think I have problems within the carb itself.

Another question, what if any role does the black idle speed knob play? Before I made the switch yesterday I had to play with it constantly to keep the bike running. Today I was able to just leave it. What's the procedure for setting this correctly and making sure the pilot circuit is working properly?

Thanks,

Waxy

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I went back to the stock 45PJ and fixed 60 PAJ. Overall, an improvement, it definitely idles better and there's very little pop on decel, I think performance in the low end is better as well.---- Normal situation is - a completely stock DRZ400E with CE runs on 2 pilot air jets: a 60 and a 90. If you pinch off the hose to the 90 (what the CE does under hi vacuum coast) at idle, the bike will die from too rich. If your bike runs on 45/60, there is something wrong. The nipple in the side with the tinnnny 90 jet is sealed , right?

If I turn it out to about 3-3.5 turns, it idles nicely. Once completely warmed up, it does have a very slight hanging idle too. ---- Yea, sounds lean.

This amazes me, I thought it would be really rich. I'm starting to think I have problems within the carb itself.-- Me too

Another question, what if any role does the black idle speed knob play?---- adjusts slide height to set idle speed.

Before I made the switch yesterday I had to play with it constantly to keep the bike running. Today I was able to just leave it. What's the procedure for setting this correctly and making sure the pilot circuit is working properly?----That does seem to be the question. With the carb off, set the slide completely closed. Now turn in the stop screw to raise the slide so about .020 gap under the slide. It should idle there and make final speed adj with engine running. If the slide is way up, like .060 to keep it running, something is wrong. Under the top cap the linkage that raises the slide is driven from the shaft. There is a jack screw and lock nut there. They need to be tight. They are the ones you remove to get the slide out, not the little phillips screw.

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.---- Normal situation is - a completely stock DRZ400E with CE runs on 2 pilot air jets: a 60 and a 90. If you pinch off the hose to the 90 (what the CE does under hi vacuum coast) at idle, the bike will die from too rich. If your bike runs on 45/60, there is something wrong. The nipple in the side with the tinnnny 90 jet is sealed , right?

There are two nipples on the side of the carb one above the other, both are sealed with rubber plugs. I checked them thoroughly last night, they seem to be sealed. I'll check them again tonight, and maybe apply a thin film of grease.

I'm not sure which other pilot air jet you're talking about. Is it the one right next to the #60 PAJ? If not, where do I locate the #90 PAJ?

That's what I figured. It should be gurgling rich on the pilot circuit now, (PAJ should be more like 80-90) and yet it's still acting rich.

What are the potential problems that could cause this? (I know the carb is sealed to the boots, and all the surfaces within the carb itself are sealed.)

---- adjusts slide height to set idle speed.

----That does seem to be the question. With the carb off, set the slide completely closed. Now turn in the stop screw to raise the slide so about .020 gap under the slide. It should idle there and make final speed adj with engine running. If the slide is way up, like .060 to keep it running, something is wrong. Under the top cap the linkage that raises the slide is driven from the shaft. There is a jack screw and lock nut there. They need to be tight. They are the ones you remove to get the slide out, not the little phillips screw.

I'll adjust the slide height to .020 tonight. I'm guessing it's pretty close to that now, maybe a little more.

Before I went back to the 45/60, I'd have to raise the slide as far as the screw would open it just to keep it running. Once it was thoroughly warmed up, then I could progressively close the slide to keep the idle speed under control.

Waxy

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Another thing that occurred to me - the choke causes the engine speed to increase, even when the bike is at normal operating temp.

Another sign of being lean?

Waxy

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The 90 pilot air jet is screwed into the end of the small nipple on the out side if the carb where one of the CE hoses went. The thread is something like 3.5mm.

Wow, hell yes the choke is a sign of lean. That baby should just chug and die when the choke is pulled on after a minute or so. Some place you are getting way too much air or way too little fuel. Your problem is not jetting. Something is wrong. Has the slide ever been out? Take it out and check the seal between the roller slide and the floating plate in front of it. And Look to see the center notch is down. Don't go by the parts blow up - it is wrong. The center notch goes down. At idle, air must pass under the slide in the center not around the edges.

Next time you have it up and running, take a propane torch (no flame) and move the propane around the carb and boots. Any vacuum leak will suck in the propane and change the engine speed. Worth a try.

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Thanks Noble.

So I'm not going crazy after all. :naughty:

Propane things sounds a little scary, but I'll give it shot.

I've never taken the slide mechanism apart, but I'll give it a whirl.

Unfortunately, I may not be able to get at it again until the weekend, maybe tomorrow after work if I'm lucky.

Thanks again, I'll keep you posted. :naughty:

Waxy

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I know we have been over this but I just want to make absolutely sure. When you removed the CE you removed 3 hoses. 1 from the head just in front of the rubber connector to the carb and 2 from the side of the carb. The hose closest to the air cleaner is an air intake to the CE. If that nipple is not plugged, you have unfiltered air entering the carb but it does not affect fuel mixture. The other nipple on the carb is where the air enters the pilot circuit. If that nipple is not plugged, air entering there goes directly into the pilot air circuit and affects low speed jetting. (just what it was designed to do with a functional CE) The 3rd nipple on the head is the control vacuum. That nipple normally is unscrewed and replaced with a 8mm bolt and copper washer to seal it up. If this nipple or hole is un-sealed it is large enough to greatly affect fuel mixture over a wide range. All 3 nipples are absolutely sealed, right? You have not run any connecting hoses between the nipples, right?

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I'm pretty darn sure they're all sealed, but I'm going to take all of the rubber plugs off and re-seal them with some sillicon as well just to be sure. I'll take some pics. Burned walked me through the CE removal process a couple of years ago, and I didn't have any problems then.

Could the problem be as simple as plugged veins in the carb? I'm thinking I might have some varnish in there or something. Even with fuel stabilizer, it's sat through four long winters.

My current plan was to completely disassemble the carb on Saturday, let it soak in varsol over night, and then blow it out with compressed air and try to start over.

The truth is, I've been riding to work the last couple days, and other than bottom end performance, it's running really well. Mid range is great, top end is a little flat, but that's likely a MJ issue, and it's idling just fine.

I kind of hate to mess with it too much, but I really want to get it solved once and for all so that I've got good consistent performance and I'm not having to take the carb off every day after work.

Thanks again,

Waxy

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I have a 2001 Dual Sported DRZ400E. Bought in Arizona and now street

licensed in CA.

The 45 pilot is great. The air jet next to it is a size 60.

I run a 158 main with FMF Exhaust and Airbox mods.

I have had the carb on and off for a year now, about 7 times!

FMF and Baja Designs websites say 45 pilot and 165 main!

38 Pilot seems REALLY Lean?

BTW, I am at about 5000 ft too, and 45 worked great.

The previous owner had it in Baja with lots of junk in the gas, and the pilot circuit kept getting plugged up. It would run with the choke ON, but not idle after turning OFF the choke. I got that fixed, but now it stumbles off Idle! If I roll it on easy, it is OK. The Pilot Plugs EASY! 3 Times now!

I have cleaned the tank and petcock twice now. Think I got it clean now,

BUT..

Now, my problem is the Accelerator Pump(AP), I THINK???

This stumble does not seem to get better with changing the FUEL Mixture screw, so I think it is the AP?

The carb is older than the ones described for the new Yamahas on ThumperTalk.

There is a brass jet called the leak jet that helps set the amount of gas during acceleration hit. I my carb the "Leak Jet" is NON removable and looks like a Square Brass Peg in a round hole? It is NOT in the bowl, but above the diaphragm in the accelerator chamber. None of the documentation is talking about my FCR39! Now Leak Jet in my bowl?

DOES ANYONE KNOW how to get this OUT????

Am I nuts? If it has junk in it, how do you clean it?

HELP!

Going Crazy in Crestline! :naughty:

(about to buy a whole new carb!)

Mike MotoDog

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Mike,

The 45 pilot is great. The air jet next to it is a size 60.---??? The air jet is a 60 but it is not next to the pilot fuel jet. That jets is a 65 and is the starter fuel jet. The 60 pilot air jet is in the air bell next to the 200 main air jet. You also have a 90 pilot air jet feeding air from the CE.

38 Pilot seems REALLY Lean?--- Not when it is used with the correct air jet and the CE removed

There is a brass jet called the leak jet that helps set the amount of gas during acceleration hit. I my carb the "Leak Jet" is NON removable and looks like a Square Brass Peg in a round hole? It is NOT in the bowl, but above the diaphragm in the accelerator chamber. None of the documentation is talking about my FCR39!---- As far as I know, you do not have a leak jet in the large body FCR carb used OEM DRZ400E. What you are describing is the check valve to admit fuel to the AP. You clean it by blasting carb cleaner thru it in the fwd flow direction

DOES ANYONE KNOW how to get this OUT???? ----- Do not remove.

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OK

New Update.

My stomach's a little queasy.

The problem just became painfully obvious. The reason I was lean was because the vacuum port on the engine was open. The rubber seal looked fine from the top, but when I checked it out, the whole thing was basically wide open underneath. I'm sick thinking about how much dirt got in there or how much damage I've done. The spark plug looked a little lean, but no aluminium, so here's hoping.

I plugged the port again with another rubber vacuum seal, but surely there must be a better way so this doesn't happen again?

Now, on to the next problem.

Once I realized what the problem was, I put everything back to as close to the "burned jetting" as I could.

148MJ

Stock needle, 5th clip

40PJ

5/8 turn PAS

2 turns fuel screw.

Set the slide height to approx. .020

Won't idle. Throttle has to be opened to start bike and keep it running (1/8-1/4). It would idle roughly with the choke on and no throttle. I turned the fuel screw screw all the way in, and it would idle slowly and kinda rough, no choke. Assume idle is too rich.

I took the carb off again and turned the PAS out to ~1 turn. Now the bike will only idle with the choke on (poorly) or if I hold the throttle open ~1/8-1/4. The fuel screw doesn't seem to have any effect at all.

I didn't goof around with the black idle speed knob.

Will the standard pilot air jet work with the 40pj so I can eliminate that variable?

What's my best bet for a pilot circuit jetting combo until I can get a 38pj?

Thanks guys,

Waxy

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you made to big of a change to the pas.

go to 3/4 turn pas with the 40 pilot.

better check the rest of your vacuum caps as well.

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Shouldn't it idle regardless of the PAS?

I don't get why it won't stay running without throttle.

If it doesn't idle with the PAS at 3/4 and the 40pj, (I have a feeling that isn't going to solve the problem) what next?

When do I start adjusting the idle speed control knob?

Waxy

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no,the pas has a drastic affect ont he mixture.with it at 5/8 turn is was to rich to idle.at 1 turn it was too lean to idle.

set the pas at 3/4 and the fuel screw at 2 turns.that will get it close enough that you should be able to make it idle with the speed screw.

at that point you can fine tune the fuel screw.

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You asked for a better way to seal the port on the cylinder head. Noble mentioned taking an 8MM bolt and a brass washer. (that was buried in the flurry of replies).

I haven't gotten the plugs yet, but I took off my coast enricher while waiting for my JD jet kit.

I'll probably use threadlocker to help seal that port - unless someone thinks it is a bad idea. Does anyone know where I can get a "handful of common bolts, nuts, washers etc?". I don't have my home junkyard set up quite enough yet after the move.

Good luck!

Richard

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